(1) Field of the Invention
This invention relates to a bonding structure using glass and solder.
(2) Description of the Related Art
Using solder at a junction is known as a related-art bonding form from, for example, JP-A No. 2009-182238 which discloses the use of solder to bond substrates to each other and the use of glass to cover a conductor layer formed on the substrate and the surface of the substrate in order to protect the conductor layer and extend the substrate life.
At present, solder including Pb is employed as a bonding material used for electrical bonding between a substrate and a conductor layer of a functional element in an area exposed to a high temperature environment of 200° C. or higher, such as in an engine room of an automobile. There is, as of now, no technique as an alternative to Sn—Pb solder including 85% or more of Pb as a bonding material capable of resisting a high temperature environment. For this reason, the use of Sn—Pb solder is allowed by the RoHS (Restriction of Hazardous substances) directive which restricts the use of substances which are considered hazardous, such as Pb and the like. However, the use of Sn—Pb solder is expected to be prohibited in the future. A problem in this case is the absence of bonding materials capable of maintaining reliable bonding over a long time period in the high temperature environment of 200° C. or higher, except for Sn—Pb solder. Under the circumstances, a bonding technique to achieve reliable bonding maintained in high temperature environment is required in place of the Sn—Pb solder technique.